annexc - Newmont Mining Corporation

Annex C5 – Soil Resources Supplemental Information C5 - 1
GEOLOGIC AND LANDFORM RELATIONSHIPS
Soil in the Proposed Mining Area developed from two principal geologic units and their
associated alluvial deposits. Soil developed on Lower Birimian rocks have the widest
distribution, while the granitic unit is far less prevalent and occurs only in the southern-most
areas within the Proposed Mining Area. Soil series occurring on similar topographic
positions in the two units exhibit similar drainage and development with comparable series
occurring in sequence from uplands to lowlands in each geology unit.
In the lower Birimian unit, the upland soil sequence begins with the red Kobeda and Bekwai
series located on upper slopes and summits. The better drained and frequently stonier
Kobeda series occurs on steep upper slopes and high summits while the Bekwai series
occurs on slightly less steep upper slopes and lower summits. The moderately-well drained,
brown Nzima series occurs lower in the landscape than Bekwai on middle to upper slopes
and low ridges. The lowland sequence begins with the imperfectly drained, yellowish brown
Kokofu series of lower-slope colluvial materials relatively free of coarse fragments with the
poorly drained, grayish brown Oda and Temang series occurring in clayey and sandy valley
bottom alluvial deposits, respectively.
The soil series developed in granitic rock are well to poorly drained, loamy to sandy
textured, and deep to very deep. Profiles have a notable amount of weather resistance
quartz that comprises the majority of the sand and coarse fragments common to soil from
this geologic unit, especially the sandy valley bottom soil. While quartz fragments are
common, concretions occur less frequently than in soil of lower Birimian origin.
The deep Swedru and Nsaba soil series occur on the upper and middle slopes of the granitic
geologic unit, respectively. The well drained Swedru series is slightly redder than the
moderately-well drained Nsaba series. The lowland sequence begins with the Akroso series.
Similar to Kokofu, this series is moderately well drained and generally free of coarse
fragments. The valley bottom soils include Nta, which occurs on very gentle lower slopes,
and Ofin, which occurs on floodplains. The profiles of the Nta and Ofin series range from
poorly to imperfectly drained and have very few coarse fragments.
SOIL SURVEY
Map units consisting of complexes and consociations were mapped within the Proposed
Mining Area as shown in Figure 3-12 (Geomatrix and Soil Research Institute (SRI) 2008).
A total of 484 soil profiles were examined at regular intervals along transects and traverses
to describe and classify the soil. Sixteen representative profiles were sampled to assess
agronomic properties. As part of a separate sampling program, surface soil samples were
collected from 73 sites for analysis of soil element concentrations. All observation points
and sample sites are shown in Figure 3-12. Additional information regarding the soil
observed at each point is provided in the 2008 soil resources technical report (Geomatrix
and SRI 2008).
Akyem Gold Mining Project November 2008 FINAL EIS